Motor vehicle with gravel detection device and method for detecting gravel

Abstract

Motor vehicle (1) with a gravel detection device (2), comprising a wheel (7) with a profiled tyre which is at least partially covered by a mudguard (5), a sensor (4, 14) mounted in an area of ​​the fender (5) for detecting stone impact, and an evaluation device (3) which, depending on one or more detected rockfalls, detects a gravel condition of a roadway to be traveled and which triggers a predetermined measure depending on the gravel condition.

Description

[0001] The invention relates to a motor vehicle with a gravel detection device and a method for detecting gravel to prevent paint damage on motor vehicles and to increase driving safety.

[0002] EP 1 867 545 A1 describes a rail vehicle with a ballast detection system. The ballast stones are carried out of a tracked ballast bed by air forces from a drag current caused by the rail vehicle or by the falling of ice accumulations in winter. Ballast stones impacting the underbody are acoustically detected by at least one sound sensor or acceleration sensor located on the underbody of the rail vehicle. The detected signals are fed to a signal processing device, which generates a ballast detection signal. The ballast detection signal indicates the impact of ballast stones on the underbody. This can be represented as the number of ballast impacts per unit of time and thus their frequency.If the ballast level exceeds a predetermined safety level, a visual and / or acoustic warning signal can be issued, and the ballast level signal can be incorporated into the rail vehicle's operating mode. In this case, the speed can be automatically reduced. Furthermore, ballast level detection can identify track sections with a high propensity for ballast level.

[0003] US 2010 / 0127133 A1 discloses a method and a device for detecting impacts of particles, in particular ballast stones, into monitored areas of a vehicle, in particular a rail vehicle. The ballast stones are carried out of a traveling ballast bed by the air suction of the rail vehicle. The impacts of the ballast stones are not detected with sound sensors, but with vibration sensors arranged in direct contact with the monitored areas. Furthermore, fast video cameras can be provided, which are aimed at the monitored areas and whose video data is temporarily stored. After one of the ballast stones impacts, the video data from the video cameras detecting the impact can be specifically evaluated.

[0004] DE 103 40 222 A1 discloses a method and a device for the theoretical assessment of the risk of damage to a motor vehicle due to stone chipping during its design phase. The assessment is performed using a data model, wherein the data model comprises a surface model for at least part of an outer surface of the motor vehicle. The risk of damage is specified at various impact points on the outer surface depending on at least one impact angle. The impact angle is the angle between the line of throw of a particle causing the stone chipping and a tangent at the impact point on the outer surface of the motor vehicle.

[0005] DE 28 27 845 A1, DE 10 2005 054 381 A1, DE 102 57 795 A1, DE 33 43 402 C2 and DE 92 00 318 U1 show different cladding elements for motor vehicles to prevent damage, in particular to the wheel housing, the underbody and / or the body components of the motor vehicle, which are exposed to impacts from particles, in particular gravel and / or chippings.

[0006] EP 0 456 164 B1, EP 2 368 781 B1 and DE 10 2004 041 090 A1 describe structural modifications, in particular by means of beading and / or impact elements for motor vehicles or rail vehicles, with which an impact of particles, in particular gravel and / or chippings, is prevented from hitting other vehicle components.

[0007] DE 198 17 567 C2, DE 298 07 563 U1 and EP 1 360 105 B1 disclose wheel arch parts or wheel house liners as mechanical devices for preventing damage to motor vehicles caused by impacts of particles, in particular gravel and / or chippings, wherein the devices additionally dampen the sound generated by the impacts.

[0008] DE 195 43 137 A1 discloses a sensor arrangement suitable for use in vehicles for detecting road surface wetting. It is mounted on a vehicle body, for example, in the area of ​​a wheelhouse interior trim, and is suitable for detecting splash water. It comprises a body that is vibrationally decoupled from the body in such a way that noises not related to road surface wetness, such as engine noise, road grit, and vibrating body parts, are not detected.

[0009] DE 42 35 809 C1 also discloses a sensor system for motor vehicles for detecting wet road surfaces. A plate sensor is mounted behind a wheel and is exposed to water droplets thrown up by the wheel while driving on wet roads. The plate sensor consists of a base plate with an accelerometer on the rear side. This generates raw signals that, after amplification and processing, indicate the wetness of the road surface.

[0010] DE 103 20 809 A1 discloses a method for detecting and monitoring vehicle movement. For this purpose, several sensors are mounted on the vehicle's chassis and body to record measured values ​​of acceleration, speed, distance, force, or noise. The measured values ​​acquired by the sensors are processed using a pattern recognition method, for example, a method known from speech processing.

[0011] The present invention is based on the object of creating a motor vehicle and a method for detecting a gravel condition of a road surface.

[0012] This object is achieved by a motor vehicle with a device and a corresponding method according to the independent patent claims. Advantageous embodiments are contained in the subclaims.

[0013] According to a first aspect of the present invention, a motor vehicle with a gravel detection device comprises a wheel with a profiled tyre that is at least partially covered by a mudguard, a sensor for mounting in an area of ​​the fender, wherein the sensor is designed to detect a stone impact in the area of ​​the fender and an evaluation device which, depending on one or more detected rockfalls, records the gravel condition of a roadway to be traveled on and which triggers a predetermined measure depending on the gravel condition.

[0014] With such a vehicle, it is possible for the first time to reliably inform a driver about the gravel condition of a road and thus about any danger to the vehicle and / or to initiate measures against rockfall, which are explained below. Using information about the gravel condition, the driver can adjust their driving behavior in such a way that damage to body components is reduced and driving safety is increased. The automatically triggered measures also serve to reduce damage to body components, thus maintaining the value of the vehicle, and increase driving safety.

[0015] High-quality vehicles feature acoustic insulation. Acoustic insulation in the fender area dampens the impact noise or vibrations of gravel particles in the event of a rockfall to such an extent that the driver can barely perceive such impact. The gravel detection system integrated into the vehicle ensures that a gravel road surface is reliably detected, allowing appropriate measures to be taken.

[0016] If gravel is present on a road, a vehicle's grip on the road surface is reduced, which impairs driving safety. Furthermore, driving over gravel particles can be stirred up, which can damage vehicle body components.

[0017] Gravel or gravel particles are solid, loose and / or granular particles, whereby the term "gravel" refers to all particles that can be driven over by a treaded tire, regardless of their consistency, such as gravel, chippings, sand, hail, sleet, fruit stones, tree fruits such as chestnuts, etc.

[0018] Gravel particles or impacting gravel that strike the body components of a motor vehicle are referred to as rock chips. Such rock chips damage the surface of body components depending on the speed, weight (mass), momentum, shape or external appearance (protruding points, sharp edges), hardness and angle of impact of the respective gravel particle, and the surface hardness of the body component.

[0019] The gravel condition describes the condition of a roadway with respect to the gravel it contains. In particular, the gravel condition can include the number of particles per surface area of ​​the roadway. This gravel condition can also be characterized by one or more of the following: consistency, size, weight (mass), shape or external appearance, and / or hardness. A hazard value for a motor vehicle can be derived from the gravel condition. The higher the gravel condition value, the greater the hazard to the vehicle from rockfall or an unstable driving situation.

[0020] The fender is a body component and may include a wheel house, which partially covers or surrounds one or more wheels of the motor vehicle, and an outer body section, which forms part of the outer skin of the motor vehicle.

[0021] The wheel housing or wheel house is the housing in which one or more wheels are located, or the recess on a pontoon body of a motor vehicle in which the wheels are arranged.

[0022] The fender area or the area of ​​the fender includes the fender itself, its fastening elements and attachments, a section of an underbody adjacent to the wheel arch with attachments such as side skirts, front apron, rear apron, etc., as well as wheel suspensions or axle structures of the motor vehicle.

[0023] In a motor vehicle with treaded tires, particles are stirred up or thrown upwards from the road surface by the mechanical action of a tire tread on the wheel, as the particle in question is caught by edges and / or cuts in the tire tread and / or carried along by adhesion to the tire. The throwing away occurs in such a way that a particle is thrown tangentially away from the tire surface. The motor vehicle collides with the upwardly thrown particle as a result of its driving movement, whereby the relative speed between the particle and the motor vehicle is determined primarily by the vehicle's traveling speed at a constant speed. When the vehicle accelerates, the tire can slip relative to the road surface, which can throw particles in the opposite direction of travel.

[0024] The state of the art described above includes sensors for detecting rockfall on rail vehicles. In rail vehicles, particles are chaotically stirred up by air suction or the aerodynamic forces of the drag stream caused by the rail vehicle. There is no active ejection of loose particles on the roadway (in this case, a rail) toward the rail vehicle body components equipped with sensors. Instead, the swirling direction of the stirred particles is directed in various directions by the vortex formation of the air suction, resulting in a significant difference in the relative motion between the rail vehicle and the particle stirred up by a treaded tire.Air turbulence also occurs in motor vehicles, but because the particles are thrown upwards and hit the fender, the flight path of the particles is so short that the air turbulence does not have a major influence on the particles hitting the motor vehicle.

[0025] Preferably, a vibration sensor, in particular a sound sensor or a vibration sensor, or a pressure sensor is provided as the sensor.

[0026] Stone chips impacting the body in the area of ​​the fender generate characteristic vibrations in the form of individual vibration pulses. These vibration pulses are structure-borne noise in the form of sound pulses, vibrations, or pressure curves of a contact pressure. Such detection of stone chips can therefore be carried out very precisely using vibration or pressure sensors. The vibration sensor is a vibration sensor that can also detect vibrations that do not represent audible sound.

[0027] Several pressure sensors can be used in the form of a sensor mat.

[0028] Using such a sensor mat, stone chips can be detected at various locations or over a larger area in the area of ​​the fender, enabling precise detection and thus improved analysis of the stone chips.

[0029] Preferably, the vibration sensor is directly coupled to the fender to detect structure-borne noise.

[0030] Since gravel often hits the fender, such a coupling can improve the detection of stone chips and thus make their evaluation more precise.

[0031] Preferably, the evaluation device comprises a vibration analysis device with which vibration pulses or vibration signals typical for stone impacts are detected and evaluated as stone impacts by the evaluation device.

[0032] By distinguishing the vibration pulses or signals typical of stone chips from those generated by the impact of other particles, such as spray from the wheel, precipitation, insects, bird droppings, etc., we ensure that only stone chips are assessed. This allows for precise evaluation of stone chips.

[0033] A vibration pulse is defined as the vibration signal of a single rockfall. Pressure curves can be processed analogously to the curves of vibration pulses or vibration signals.

[0034] In a further embodiment, the motor vehicle has a movable baffle plate which is movable depending on a stone impact detected by the gravel detection device.

[0035] If rockfall is detected, the impact plate can be moved to prevent it from hitting the vehicle's body by shielding these body components from the impact. The impact plate thus blocks the trajectory of the gravel particles, so that instead of hitting and damaging the sensitive surfaces of body components, they hit the impact plate. The impact plate or impact plate is preferably made of a shock-absorbing material so that the particles rebound with less energy, thus reducing their kinetic energy.

[0036] Preferably, the motor vehicle has an output device for outputting an optical and / or acoustic warning signal.

[0037] By issuing such a warning signal, the driver is informed of the occurrence of a rockfall and can take further measures, such as changing lanes, reducing speed, and / or increasing the distance to the vehicle in front, in order to reduce the number of rockfalls impacting their vehicle and increase driving safety. In addition, the warning signal can also provide the driver with information about the type, momentum, and / or number of rockfalls. This allows the driver to be informed, for example, of a severe rockfall with high impact energy as well as of an interval of several small rockfalls in close succession.

[0038] A method according to the invention for detecting gravel for a motor vehicle utilizes a gravel detection device. The gravel detection device comprises a sensor mounted in an area of ​​a fender of a motor vehicle, with the fender partially covering a profiled tire of a wheel of the motor vehicle. The sensor detects stone chips in the area of ​​the fender. An evaluation device records the gravel condition of a roadway based on one or more detected stone chips, and a predetermined action is triggered based on the gravel condition.

[0039] The predetermined measure may include one or more of the following measures: - Issue a warning message, - maximum straightening of the wheels, - Adapting the steering wheel control to indirect steering transmission, - Reduction of driving speed, - Reduction of maximum drive torques, - Increasing the distance to the vehicle in front, - Checking lanes and changing lanes if necessary, - Extension of a baffle plate, - Sending a message to other vehicles and / or to an external server, where the message describes the gravel condition.

[0040] By issuing a warning message, the driver is informed about rockfall so that he can take measures as already explained above.

[0041] By keeping the wheels as straight as possible, it is largely possible to prevent gravel particles from being thrown sideways in such a way that they damage the vehicle's body components located on the side, such as the doors, side skirts, etc.

[0042] By adapting the steering wheel control to indirect steering transmission, unnecessary steering movements are avoided, thus reducing the number of gravel particles thrown sideways. Furthermore, indirect steering transmission increases driving safety by slightly dampening abrupt steering movements—i.e., reducing the speed and deflection—and transmitting them to the steered wheels. This reduces the risk of lateral acceleration forces exceeding the vehicle's grip on the road surface, resulting in unstable driving.

[0043] Reducing the driving speed or reducing the maximum drive torque reduces the number of gravel particles thrown off the road, as well as their speed and thus their impact intensity. Reducing the driving speed also improves driving safety during braking and steering maneuvers, and reducing the maximum drive torque improves driving safety during acceleration. This makes it less likely that longitudinal acceleration forces will exceed the vehicle's grip on the road.

[0044] Increasing the distance to the vehicle in front reduces the probability of impact from gravel particles thrown by the vehicle in front.

[0045] If there are adjacent or contiguous lanes leading in the same direction, the vehicle can automatically change lanes after checking whether the adjacent lane is clear of other road users. The presence of gravel can be detected again in the adjacent lane, and if the adjacent lane contains more gravel, the vehicle can return to the original lane.

[0046] By extending a baffle plate, the surface of the vehicle's body components is protected, as already explained above.

[0047] Sending a message to other vehicles and / or to an external server, including the gravel condition, serves to provide information and thus preserve the value and driving safety of vehicles of following or other road users. The message can be transmitted in a car-to-car communication and / or to an external server for subsequent processing, particularly for route planning processes.

[0048] The measures explained above can therefore serve to maintain the value and / or driving safety of your own vehicle and / or the vehicles of other road users in areas where there is a risk of gravel particles.

[0049] Preferably, the evaluation device triggers the predetermined measure depending on the intensity and / or frequency of detected rockfalls.

[0050] This ensures that the predetermined measure is only triggered when the gravel condition of the road section or location traveled through has exceeded a predetermined threshold.

[0051] The evaluation device records and stores a vibration signal generated by the sensor within a predetermined time interval or over a predetermined distance. The evaluation device then compares the stored vibration signal with stored vibration patterns of rockfalls using a pattern comparison to determine one or more vibration patterns similar to the vibration signal, with ballast conditions being assigned to the stored vibration patterns. The evaluation device then determines the ballast condition of the roadway based on the ballast conditions of the similar vibration pattern(s).

[0052] The term “vibration pattern” refers to patterns of oscillations, such as sounds, noises, vibrations, shocks, and patterns of pressure curves.

[0053] Additionally or alternatively, the evaluation system can record vibration pulses from individual rockfalls and link them to the vehicle speed. The evaluation system then statistically analyzes several vibration pulses, particularly with regard to their frequency, average rockfall intensity, and average rockfall speed, in order to determine the ballast condition from the statistical parameters determined from these data.

[0054] Through pattern comparison and / or statistical evaluation, the gravel condition of a roadway can be precisely determined.

[0055] The impact velocity is the relative speed between the motor vehicle and the particle impacting the motor vehicle.

[0056] Preferably, the method for detecting gravel is used in the above-explained motor vehicle provided with the gravel detection device.

[0057] The invention is explained in more detail below by way of example with reference to the drawings. The drawings show: Fig. 1 schematically shows the structure of a motor vehicle with a gravel detection device, Fig. 2 schematically shows a rear section of a motor vehicle with a gravel detection device, Fig. 3A, Fig. 3B shows a method for detecting gravel for a motor vehicle with a gravel detection device in a flowchart, Fig. 4 schematically shows a motor vehicle moving forward in a side view, and Fig. 5 schematically shows two motor vehicles moving one behind the other and forward in a side view.

[0058] A first embodiment of a motor vehicle with a gravel detection device for detecting gravel is explained below.

[0059] A motor vehicle 1 is provided with a gravel detection device 2 for detecting gravel particles striking the motor vehicle 1 ( Fig. 1, Fig. 2). The ballast detection device 2 has an evaluation device 3, which is a computer with a CPU memory device and suitable interfaces and centrally controls the ballast detection device 2.

[0060] The gravel detection device 2 has a vibration sensor 4, which is designed as a sound sensor or vibration sensor and is connected to the evaluation device 3. The vibration sensor 4 is arranged in a fender 5. The fender 5 comprises a wheel housing 6, which partially covers a wheel 7 of the motor vehicle 1, and an outer body section 8, which forms part of the outer skin of the motor vehicle 1. The vibration sensor 4 is coupled to the peripheral surface of the wheel housing 6 and detects its structure-borne sound. When a particle 9 strikes the motor vehicle 1, acoustic signals are generated in the area of ​​the fender 5.

[0061] The area of ​​the fender monitored by the vibration sensor 4 includes the fender 5 itself, its fastening elements and attachments, a section of an underbody adjacent to the wheel arch 6 with attachments such as side skirts, front apron, rear apron, as well as wheel suspensions or axle structures of the motor vehicle 1.

[0062] The gravel detection device 2 has a storage device 10 connected to the evaluation device 3. A database is stored in the storage device 10, in which descriptive information for different particles 9 that can impact the body components is stored as particle information, linked to associated evaluation information. The particle information includes, in particular, vibration patterns that are characteristic of impacting gravel particles. The associated evaluation information includes information that describes the gravel condition, the damage to the respective body component caused by impacting particles 9, and / or the impairment of driving safety caused by the respective particles 9. Furthermore, measurement data of impacting particles 9, acquired during the journey, can be stored in the storage device 10 with further parameters as stone chip information.

[0063] Software modules are stored and executable on the evaluation device 3. The software modules comprise a detection module and an evaluation module. The detection module is designed to receive the vibration pulses or vibration signals detected by the vibration sensors 4 and, linked with other parameters, store them in the storage device 10 as stone impact information. The evaluation module is designed to read the stone impact information stored in the storage device 10 and analyze it using the particle information stored there, and evaluate it with the associated evaluation information stored there. These software modules constitute a vibration analysis device.

[0064] The detection module stores the vibration pulses or vibration signals with the following parameters, whose parameter values ​​are detected at the time of occurrence of the vibration pulse or vibration signal, as rockfall information in the storage device 10: - at least one vibration parameter, - Time (time stamp), if applicable with date, - Speed ​​of the motor vehicle 1.

[0065] The vibration parameter is a parameter that describes the vibration, such as the sound (frequency or frequency response), the volume (maximum and / or average) or the damping.

[0066] The time is read by the recording module from an on-board clock (not shown) of the motor vehicle 1, to which the evaluation device 3 is connected via a data connection.

[0067] Furthermore, the evaluation device 3 is connected to a speed sensor 11 with which the motor vehicle 1 is equipped. The speed of the motor vehicle 1 at the time of the vibration pulse or vibration signal is stored by the detection module and can thus be incorporated into the analysis or evaluation of the stone impact information by the evaluation module.

[0068] Furthermore, the evaluation device 3 is connected to output devices in the form of a display device 12 (optical output device) and / or a loudspeaker 13 (acoustic output device), which are located in the interior of the motor vehicle 1.

[0069] A method for detecting gravel for the motor vehicle 1, which is provided with the above-explained gravel detection device 2, is explained in more detail below, wherein the method is carried out by means of the above-explained gravel detection device 2. The method for detecting gravel comprises two sub-methods ( Fig. 3A and Fig. 3B), where the Fig. 3A shown part of the process from the acquisition module and the Fig. The part of the procedure shown in Figure 3B is carried out by the evaluation module.

[0070] The procedure performed by the acquisition module is explained below ( Fig. 3A).

[0071] The method begins in step S1. If, in step S2, a particle 9 strikes the body of the motor vehicle 1 in the area of ​​the fender 5, the resulting vibration pulse is detected by the vibration sensor 4 and transmitted to the detection module of the evaluation device 3. If, in step S2, the volume of the vibration pulse of the particle 9 exceeds a predetermined trigger threshold, the detection module is triggered such that step S3 is executed.

[0072] The volume of the trigger threshold is greater than background noise caused by driving and engine noise, but low enough to reliably detect impacting particles 9.

[0073] In step S3, the detection module records the course of the vibration signal transmitted by the vibration sensor 4 in the storage device 10 for a predetermined time interval or stores it in the storage device 10 and determines further parameters. The course of the vibration signal is sampled and digitized for storage. The length of the predetermined time interval is constant or can be determined depending on the vehicle speed. During the time interval, all vibration pulses of the particles 9 impacting during this time interval are recorded or stored. The further parameters determined by the detection module are the time of day and the speed of the motor vehicle 1. The recorded vibration signal, linked to these further parameters, represents stone impact information.

[0074] Thereafter, step S4 is executed, in which the acquisition module stops recording the vibration signal and stores it in the memory device 10 as a tuple linked to the other parameters as rockfall information.

[0075] Then, step S5 is executed, in which a check is carried out to determine whether operation should be continued. If operation should be continued, step S2 is executed again. If operation should not be continued, the method ends in step S6.

[0076] If it is determined in step S2 that no vibration pulse or detected vibration signal detected by the vibration sensor 4 is transmitted, ie that the detection module is not triggered, the method proceeds directly to step S5.

[0077] The procedure carried out by the evaluation module is explained below ( Fig. 3B).

[0078] The method begins in step S10. In step S11, the evaluation module reads the stone impact information stored in the storage device 10 and cleans the memory by removing outdated stone impact information from the storage device 10. Outdated stone impact information is stone impact information that was acquired at a time more than a predetermined time period ago. The time difference exceeded here can be determined by the evaluation module depending on the current speed of the motor vehicle 1. Preferably, the time difference comprises a time interval of 0.1 s to 10 s. The memory cleanup ensures that only stone impact information relevant to the current position of the motor vehicle 1 remains and is evaluated in the storage device 10, while at the same time preventing the memory device 10 from being overflowed by the stored stone impact information.

[0079] This is followed by the execution of step S12, in which the evaluation module analyses the (relevant) rockfall information stored in the storage device 10 and calculates a gravel condition for the roadway on which the motor vehicle 1 is moving.

[0080] To analyze the rockfall information, the evaluation module reads it from the storage device 10. Furthermore, the evaluation module reads the particle information, which includes, in particular, vibration patterns for impacting gravel particles.

[0081] Stone chips, precipitation, or other particles that impact a body component are distinguished by the resulting vibration signal characteristic of the respective particle type, which can be described by sound (frequency or frequency curve), volume (amplitude), and damping, as well as the resulting vibration pattern. A stone chip is the impact of one or more gravel particles, such as gravel, chippings, sand, hail, sleet, fruit stones, tree fruits such as chestnuts, etc. The vibration patterns can be used to distinguish stone chips from other impacting particles that do not pose a threat to the motor vehicle 1, such as water droplets (from rain, spray, etc.).

[0082] The vibration patterns can be determined by empirically recording vibrations such as sounds, noises, vibrations, shocks, and impacting particles 9, e.g., by driving over various particles 9 lying on different road types at different vehicle speeds and recording the resulting vibration patterns. The vibration patterns are stored together with other parameters, such as the vehicle speed, the type of particle 9 or gravel particle (gravel, chippings, sand, hail, sleet, fruit stones, tree fruits such as chestnuts, etc.) and their number per road surface, as well as with evaluation information that includes the gravel condition.

[0083] The parameters sound (frequency or frequency response), volume (amplitude) and damping depend on various other parameters such as stone impact speed and stone impact angle of the respective particle 9, its weight (mass), momentum, shape or external configuration, hardness as well as surface hardness and damping value of the body component onto which the particle 9 impacts.

[0084] Due to the non-slipping wheel 7, particles 9 lying on the road surface, in particular gravel particles, are moved upwards and partially in the direction of travel of the motor vehicle 1 by the mechanical action of the tire tread and / or adhesion to the tire. If a particle 9 is lifted or stirred up sufficiently high in the trajectory of body components of the motor vehicle 1, it will impact the respective body component. "Sufficiently high" here means that the particle 9 is accelerated downwards by gravity and therefore must be lifted to a certain height in order to impact the motor vehicle 1.

[0085] Using a simulation similar to the method described in DE 103 40 222 A1, the areas most at risk from stone impact and / or where stone impacts predominantly occur can be identified during the design phase. Such stone impact areas can be identified based on the distribution of stone impacts in the computer-aided simulation and verified using empirical methods using prototypes. Structural sound measurements can be performed in these stone impact areas. Preferably, such structural sound measurements are performed at least in the area of ​​the wheel house 6. Using the structural sound measurements, in particular, the attenuation and reflection values ​​of each individual body component can be determined at the respective points where particles impact.

[0086] The rockfall velocity is the relative speed between the motor vehicle 1 and the respective particle 9. The higher the rockfall velocity, the greater the momentum of the impacting particle 9 and thus the loudness of the impact. The rockfall velocity is significantly influenced by the vehicle speed, since the motor vehicle 1 is moving toward the sufficiently high particle 9, and the vehicle speed is significantly greater than the particle speed.

[0087] By comparing the recorded vibration signals with the stored vibration patterns, the evaluation module determines whether the vibration signal is caused by rockfall or not. The evaluation module compares all recordings in the storage device 10 individually with the stored vibration patterns. If the respective vibration signal is caused by rockfall, it determines which type of gravel particle it originates from. To increase accuracy, the evaluation module can also combine several consecutive recordings and compare the combined recording with the stored vibration patterns.The stored vibration patterns recorded at predetermined speeds are interpolated in terms of recording length, rockfall intensity (amplitude), sound (frequency) and / or rockfall frequency during pattern comparison until at least one of the different vibration patterns approximately corresponds to or is similar to the pattern of the recorded vibration signal.

[0088] The vibration patterns are stored as evaluation information, linked to the respective vehicle speed and the respective ballast condition. The evaluation module reads this information from the storage device 10 for the similar vibration pattern and thus determines the ballast condition.

[0089] If the vehicle speed stored with the matching vibration pattern differs from the vehicle speed stored with the vibration signal, the evaluation module can determine the ballast condition by interpolating the ballast condition value of the similar vibration pattern using the associated vehicle speed to the vehicle speed stored with the vibration signal. During the interpolation, the evaluation module can also include other similar vibration patterns, e.g., those with the same type of particles 9 as the similar vibration pattern, in the interpolation of the ballast condition.

[0090] The process then proceeds to step S13, in which the evaluation module checks whether or not there is a risk to motor vehicle 1 from rockfall. For this purpose, the gravel condition is evaluated in relation to the vehicle speed.

[0091] If the assessment module determines that there is a risk of rockfall, step S14 is executed, in which the assessment module initiates predetermined measures to reduce the risk of rockfall. The assessment module outputs a warning message on the display device 12 and / or loudspeaker 13 to inform the driver of the rockfall so that they can take further action.

[0092] Step S15 is then executed, in which it is checked whether operation should be continued. If operation should be continued, step S11 is executed again. If operation should not be continued, the method ends in step S16.

[0093] If the evaluation module determines in step S13 that there is no danger from rockfall, the process proceeds to step S17, in which previously initiated measures are reset or revoked. The warning message on the display device 12 and / or loudspeaker 13 is terminated. If no measures were initiated or no measures need to be reset or revoked, the evaluation module does not perform any action at this point.

[0094] After the execution of step S17, step S15 is executed.

[0095] If the motor vehicle 1 is stationary during a journey, e.g. at a red traffic light or in a traffic jam, the memory is not cleared in step S11 in order to be able to determine a gravel condition for a period of time or a distance immediately before the motor vehicle 1 came to a standstill.

[0096] A second embodiment of a motor vehicle 1 with a gravel detection device is explained below.

[0097] This embodiment is similar to the first embodiment and includes the same devices, apparatus, devices, etc., with the same reference numerals being used for the same parts as those already explained above. Fig. 1, the additional sensors of the second embodiment are connected to the evaluation device 3 with a dashed line.

[0098] The vibration sensor 4 of the first embodiment can also be omitted in this embodiment.

[0099] The evaluation device 3 is connected to a sensor mat 14, which comprises several pressure sensors (not shown) ( Fig. 1 and Fig. 2). The sensor mat 14 is arranged in the wheel housing 6 such that it covers the wheel 7 at least in part. Preferably, the sensor mat 14 is arranged in the rear area of ​​the wheel housing 6 above the wheel 7 and / or behind the wheel 7, thus covering the rear area of ​​the wheel 7, since most particles 9 impact the rear area of ​​the wheel housing 6 when the motor vehicle 1 is traveling forward. If a particle 9 thrown from the wheel 7 impacts the sensor mat 14, one or more of the pressure sensors contained therein, when a corresponding pressure has occurred, outputs an electrical signal to the evaluation device 3, which is proportional to the pressure that has occurred or to its profile.

[0100] The pattern matching method explained above for the vibration sensors 4 can be performed correspondingly with the sensor mat 14. The pressure signal curve corresponds to the vibration signal curve and is also sampled and digitized for storage.

[0101] If the sensor mat 14 comprises several pressure sensors, the course of the pressure signal of each individual pressure sensor or the courses of the pressure signals of several pressure sensors combined with one another can be recorded and / or evaluated.

[0102] Preferably, for the method explained above, the curves of the pressure signals of several pressure sensors are recorded, stored and evaluated in combination by means of pattern comparison, while preferably when carrying out the statistical method explained further below, the curves of the pressure signals of several pressure sensors are recorded, stored and evaluated individually.

[0103] The advantage of using the sensor mat 14 over the vibration sensor 4 is that, with a suitable selection of the pressure sensors and the material of the sensor mat 14, the pressure signal is less complex than the vibration signal, since the pressure signal exhibits no or less reflections and / or resonances. Especially with mechanically rigid pressure sensors, natural vibrations or post-oscillation effects occur only minimally. Since the sensor mat 14, as a flexible component, often has higher damping values ​​than the fender 5, any reflections and resonances that occur are reduced.

[0104] A further advantage of the sensor mat 14 with multiple pressure sensors is that the location of impacting particles 9 on the sensor mat 14 can be detected and stored. The location of a pressure sensor that has detected a stone impact represents the location of the stone impact.

[0105] The stone impact location of a particle 9 depends on the location at which the particle 9 leaves the wheel 7. At a constant vehicle speed, the stone impact location is therefore essentially determined by tire properties and particle properties, such as air resistance and weight (mass). The stone impact locations, and in particular their distribution on the sensor mat 14 when multiple particles 9 impact, can therefore be empirically determined in advance for each individual particle type and stored in the storage device 10 in order to be taken into account when determining the particle type in step S12. The stone impact location can be evaluated, in particular, using the statistical method for determining particle properties explained below.

[0106] The devices and methods for detecting gravel explained above can be modified in many different ways, some of which are explained below.

[0107] As an alternative to the pattern comparison explained above, individual rockfalls and their temporal progression can be statistically evaluated and, based on the statistical evaluation, a calculation of the gravel condition and hazard value can be made, as explained below.

[0108] In step S3, the detection module individually records the vibration pulses of the particles 9 impacting the motor vehicle 1. The vibration pulses of the individual particles 9 are digitized and stored individually as stone impact information together with a timestamp in a tuple in the storage device 10. The tuple can additionally include further parameters, such as vehicle speed, location of the motor vehicle 1 and / or the stone impact location of the particle 9 on the motor vehicle 1. The vehicle speed can also be stored as a function of speed versus time. The speed can then later be assigned to the individual tuples based on the stored time and the speed function. Alternatively, the vehicle speed can also be stored in such a way that the speed value or the speed function can be assigned to multiple tuples.The location of the motor vehicle 1 is read by a navigation device 15 which is connected to the evaluation device 3.

[0109] The vibration pulses of the individual impacts of particles 9, which are stored in the storage device 10, are first analyzed by the evaluation module in step S12, whereby their sound (frequency or frequency curve), volume (amplitude) and / or damping are determined as maximum and / or average values.

[0110] In the following, dependencies are explained which serve as a basis for the statistical evaluation of the individual oscillation pulses and can be quantitatively determined using previously determined empirical data.

[0111] As already explained above, the vehicle speed is the primary determining factor for stone impact speed. A higher stone impact speed causes greater damage to the body components than a lower stone impact speed. The stone impact speed determines the stone impact intensity (impulse) and thus the volume (amplitude) of impacting particles 9. Therefore, the stone impact intensity and the volume of impacting particles 9 are proportional to the vehicle speed. The average volume of the vibration pulses, which is dependent on the vehicle speed, can be used to determine the average mass of the impacting particles 9. The distribution of the volume of the vibration pulses can be used to determine the mass distribution of the impacting particles 9.

[0112] The type of particle can be determined from the mean mass and the mass distribution or from the mean mass and the frequency of impacts.

[0113] As motor vehicle 1 travels faster, the rotational speed of wheels 7 increases, and more particles 9 are lifted or swirled up from the road surface, and these particles are lifted higher. Consequently, at higher vehicle speeds, more particles impact motor vehicle 1 per unit of time than at lower vehicle speeds. The number of particles 9 that are moved upwards or swirled up and thus impact per unit of time is therefore proportional to the vehicle speed.

[0114] This means that the vibration pulses or vibration signals can be evaluated depending on the speed.

[0115] Due to their higher mass, heavier particles 9 are not moved or whirled up as far as lighter particles 9. The number of particles 9 moved upwards and thus impacting per unit of time is therefore inversely proportional to the particle weight (particle mass).

[0116] The more liftable particles 9 are on the road, the more particles 9 impact the motor vehicle 1. The number of impacting particles 9 per unit of time is therefore proportional to the number of particles 9 on the road.

[0117] The number of impacting particles 9 per unit of time depends on other parameters or properties, such as tire geometry, vehicle geometry, adhesion to the tire (material, temperature, humidity), friction of the wheel, etc.

[0118] In particular, the stone impact location on motor vehicle 1 depends on the location at which the respective particle 9 exits the tire. The respective stone impact location is characteristic of the respective particle type and its size or weight (mass). The distribution of stone impact locations thus depends on the respective particle type. Such distributions can be determined empirically for each particle type and the respective tire or tire type used.

[0119] The frequency of impacts of particles 9, their average mass, and the vehicle speed allow us to determine the number of particles 9 per area on the road. The number of particles 9 per area on the road is proportional to the frequency of impacts. The lower the average mass of particles 9, the more particles 9 are lifted and the more particles 9 impact motor vehicle 1. The higher the vehicle speed, the more particles 9 impact motor vehicle 1.

[0120] From the relationships explained above, regulations or calculation steps can be extracted by means of which the statistical evaluation of the individual vibration pulses is carried out and from this the gravel condition of the roadway and the hazard value for motor vehicle 1 are calculated.

[0121] This allows several vibration pulses to be statistically analyzed, particularly with regard to their frequency, average rockfall intensity, and average rockfall velocity, to determine the gravel condition based on the statistical parameters discussed above. Key parameters for the gravel condition are the number of particles 9 per unit area on the road surface and their average mass.

[0122] The hazard value is determined primarily by the rockfall speed and the average mass of the particles 9, ie the rockfall intensity.

[0123] Further variations are explained below.

[0124] Preferably, all wheel arches 6 of all wheels 7 are provided with vibration sensors 4 and / or with sensor mats 14, since then all impacting particles 9 can be reliably detected.

[0125] Multiple vibration sensors 4 and / or multiple sensor mats 14 can be provided on the left and right sides of the vehicle. If such sensors are present on the left and right sides of the vehicle, then by comparing the stone chips detected on the respective sides of the vehicle, it can be determined whether the entire roadway, or only a left or right section of the roadway, is contaminated with gravel. Likewise, stone chip information and the gravel condition can be determined individually for the left and right sections of the roadway. This information can also be transmitted as a message, as explained further below.

[0126] Additionally or alternatively, the rotational speeds of the wheels 7 can be detected by wheel speed sensors and received by the evaluation device 3, stored, and taken into account in the evaluation. In particular, slipping wheels 7 can be detected, and particles 9 impacting at higher speed can be taken into account when assessing the gravel condition or the danger to the motor vehicle 1.

[0127] If several vibration sensors 4 are provided on the motor vehicle 1 in the area of ​​a fender 5 or in the wheel house 6, the detection module can additionally determine the approximate stone impact locations of the impacting particles 9 by measuring the propagation time of the vibration signals and store them in the storage device 10 in step S3.

[0128] If the stone impact locations are recorded, data describing the body components can also be stored in the storage device 10, indicating the damage potential for each body component or for each area of ​​a body component. This allows the evaluation device in step S13 to estimate the expected damage to the body components through extrapolation.

[0129] In addition, the rockfall locations and in particular their distribution when several particles 9 impact can be determined empirically in advance for each individual particle type and taken into account when determining the particle type in step S12.

[0130] Alternatively, steps S11 and S12 can also be performed together in one step, thereby reducing the number of required memory accesses.

[0131] Alternatively, a simple determination of the gravel condition can be carried out by counting the number of entries of relevant rockfall information in the storage device 10 during the detection and storage of individual vibration pulses and combining this with the inverse of the vehicle speed.

[0132] Pattern matching can be combined with statistical analysis to determine the ballast condition more precisely. For this purpose, both the vibration signal generated by the entire impacting particles 9 and the vibration pulses generated by the individual particles 9 are preferably recorded and stored in the storage device 10 and further processed, as explained above. Alternatively, the vibration signal of the entire impacting particles can be combined from the vibration pulses recorded by the individual particles 9 based on their time stamps.

[0133] In Fig. 1, the additional devices or equipment of the modifications are connected to the evaluation device 3 with a dotted line.

[0134] If the evaluation device 3 is additionally connected to the navigation device 15, it can record the course of the vibration signal over a predetermined distance instead of a predetermined time interval in step S3. The length of the predetermined distance is constant or can be determined depending on the vehicle speed.

[0135] If the evaluation device 3 is additionally connected to the navigation device 15, the detection module can determine the respective location of the motor vehicle 1 at which a stone impact occurred from the navigation device 15 in step S3 and store it together with the other parameters as stone impact information in the storage device 10 in step S4. Such stored location information can be used by the evaluation module to remove stone impact information from the storage device 10 in step S11 if the current location of the motor vehicle 1 differs significantly from the location at which the stone impact occurred, as explained above for outdated stone impact information. For this purpose, the evaluation module can access the current location of the motor vehicle 1 from the navigation device 15 in step S11. Furthermore, such stored location information can be used for the statistical evaluation explained above.

[0136] In addition, the evaluation device 3 can be connected to one or more driver assistance systems 16, such as a steering wheel control, a drive control or an engine control, a distance warning device and / or a lane change assistant, wherein the corresponding driver assistance system 16 is requested by the evaluation module of the evaluation device 3 in step S14, depending on the risk of stone chipping, to initiate one or more of the following measures as a predetermined measure: - maximum straightening of the wheels, - Adapting the steering wheel control to indirect steering transmission, - Reduction of driving speed, - Reduction of maximum drive torques, - Increasing the distance to the vehicle in front, - Check the lanes for gravel condition and change lanes if necessary.

[0137] By straightening the wheels 7 as far as possible using the steering wheel control, it is largely possible to prevent gravel particles from being thrown sideways in such a way that they damage body components arranged laterally on the motor vehicle 1, such as the doors, the side sills, etc.

[0138] By adapting the steering wheel control to indirect steering transmission, unnecessary steering movements are avoided, thus reducing the effects of gravel particles thrown sideways. Furthermore, indirect steering transmission increases driving safety by slightly dampening abrupt steering movements, i.e., reducing their speed and deflection, and transmitting them to the steered wheels 7 of motor vehicle 1. This increases the grip of motor vehicle 1 on the road surface.

[0139] Reducing the driving speed or reducing the maximum drive torque via the drive control or engine control reduces the number and speed of thrown gravel particles, and thus also their impact intensity. Reducing the speed also improves driving safety during braking and steering, and reducing the maximum drive torque improves driving safety during acceleration.

[0140] Increasing the distance to the vehicle in front using the distance warning device reduces the probability of impact from gravel particles thrown by the vehicle in front.

[0141] If adjacent or contiguous lanes exist, i.e., lanes leading in the same direction, vehicle 1 can use the lane change assistant to check whether the adjacent lane is clear of other road users and, if it is, automatically change lanes. The presence of gravel is again detected in the adjacent lane, and if the adjacent lane contains more gravel, the vehicle returns to the original lane.

[0142] If the driver assistance system 16 connected to the evaluation device 3 is a distance warning device, the detection module can determine the distance to a preceding vehicle from the distance warning device in step S3 and store it in step S4 as part of the stone impact information in the storage device 10. This stored distance can then be read by the evaluation module in step S12 and taken into account when determining the hazard value. The shorter the distance to the preceding vehicle 1, the greater the hazard posed by ejected particles 9.

[0143] Additionally, the evaluation device 3 can be connected to a radio communication device 17, via which the evaluation device 3 transmits and / or receives the gravel condition to other motor vehicles 1 in the immediate vicinity of the motor vehicle 1 in the event of a rockfall hazard in step S14, for example, using car-to-car communication, and initiates appropriate measures in the event of a hazard. Sending a message to other vehicles, describing the gravel condition, serves to inform and thus maintain the value of the motor vehicles 1 of other road users and their driving safety.

[0144] If the evaluation device 3 is connected to the radio communication device 17, the evaluation device 3 can transmit the detected stone impact information to other motor vehicles 1 in the vicinity of the motor vehicle 1, for example using car-to-car communication, and / or receive it from them before it is removed from the storage device 10 as outdated stone impact information in step S11, and can initiate appropriate measures in the event of a hazard.

[0145] In addition, if the evaluation device 3 is connected to the navigation device 15 and the radio communication device 17, it can transmit and / or receive the gravel condition for a planned or to-be-traveled route, for an upcoming route section, or for the current location of the motor vehicle 1, to an external server. During route planning, the evaluation device 3 can then output a warning on the output device 12, 13 if it receives a hazardous gravel condition for the route to be traveled and suggest calculating an alternative route on the navigation device 15.

[0146] If the evaluation device 3 is connected to the navigation device 15 and the radio communication device 17, it can transmit recorded rockfall information, together with the location of the motor vehicle 1 at which the rockfall information was recorded, to the external server before it is removed from the storage device 10 as outdated rockfall information in step S11 and / or receive rockfall information from the external server for transmitted locations and / or routes.

[0147] Additionally, if the evaluation device 3 is connected to the lane change assistant as a driver assistance system 16 and the radio communication unit 17, it can receive the gravel condition of oncoming traffic via car-to-car communication and, depending on the gravel condition, change to an outside or further outside lane in order to increase the distance to oncoming traffic and thus reduce the impact of gravel particles. Information from other impacting particles that do not pose a danger to the motor vehicle 1, such as water droplets that are stirred up as spray on a wet road surface, can also be transmitted, for example, using car-to-car communication. By transmitting such information, the lane change assistant can also change lanes if visibility is obstructed by spray.

[0148] In addition, all stone chips that, due to their parameters such as stone chip speed, weight (mass), stone chip intensity (impulse), type of stone chip, etc., pose a threat to the individual body components they impacted can be permanently stored in the storage device 10 for later retrieval and, if necessary, erased. This allows a damage pattern comprising the surface sections of the motor vehicle 1 damaged by stone chips to be automatically stored by the gravel detection device 2 and, if necessary, transmitted to a workshop, such as a body shop, a leasing or rental vehicle company, and / or an insurance company.

[0149] Additionally, the evaluation device 3 can be connected to an outside thermometer (not shown) and / or a precipitation sensor (not shown) or, if connected to the navigation device 15 and the radio communication device 17, can retrieve corresponding weather data for the current vehicle position from the Internet. By taking precipitation data or the outside temperature into account, since this temperature falls during precipitation, rockfalls and precipitation such as hail, rain, sleet, etc., can be more precisely differentiated.

[0150] In addition, the evaluation device 3 can be connected to one or more servomotors 18. With each servomotor 18, one or more baffles 19 are extended from or retracted into the body of the motor vehicle 1 ( Fig. 2).

[0151] Here, Fig. 2 shows that the actuator 18 / 1 moves the baffle plate 19 / 1 in an extension direction 20 / 1, the actuator 18 / 2 moves the baffle plate 19 / 2 in an extension direction 20 / 2, and the actuator 18 / 3 moves the baffle plate 19 / 3 in an extension direction 20 / 3 out of the body of the motor vehicle 1. While the baffles 19 / 1 and 19 / 2 are extended linearly, the baffle plate 19 / 3 is pivoted out by an angle of attack relative to the motor vehicle 1. Accordingly, the actuators 18 / 1, 18 / 2, and 18 / 3 retract or pivot the respective baffle plate 19 / 1, 19 / 2, and 19 / 3 back into the body of the motor vehicle 1 against the respective extension direction 20 / 1, 20 / 2, and 20 / 3.

[0152] Such a baffle plate 19 serves to shield or protect the body components of the motor vehicle 1 and / or other motor vehicles 1 in the near field of the motor vehicle 1 against ejected particles 9, in particular gravel particles, by moving the baffle plate 19 into the trajectory 21 of the ejected particle 9 and thus blocking its trajectory 21. The extension distance of the baffle plates 19 / 1 and 19 / 2 as well as the angle of attack of the baffle plate 19 / 3 can be varied depending on the condition of the gravel, the frequency of rockfalls, the weight (mass) of the rockfalls, the rockfall speed and / or the vehicle speed. Preferably, in the case of frequent impact of particles 9, impact of particles 9 with a high weight and / or high rockfall speed or high vehicle speed, the baffle plates 19 are extended or retracted further.- pivoted, whereas in the case of low impact of particles 9, impact of particles 9 with low weight and / or low stone impact speed or low vehicle speed, they are extended or pivoted to a lesser extent. In . Fig. 2 shows several ejected particles 9, whose trajectories 21 are blocked by the respective impact plates 19. Further ejected particles 9 are shown with a trajectory 21 that causes the ejected particles 9 to impact the fender 5 or the wheel housing 6 formed by it, so that a vibration sensor 4 and / or a sensor mat 14 detects the stone impact.

[0153] The trajectories 21 with respect to the motor vehicle 1 moving forward in the direction of travel 22 are only shown approximately, since the inertial system in Fig. 2 is that of the wheel 7 and the trajectories 21 are shown tangentially away from the wheel 7 without having a directional component resulting from the direction of travel of the motor vehicle 1.

[0154] Both procedures explained above, which are used in the Fig. 3A and Fig. 3B can also be executed sequentially as a common method by a software module stored in the evaluation device 3.

[0155] Fig. 4 schematically shows a motor vehicle 1 in a side view, showing which body components can be impacted by particles 9 thrown off given a corresponding trajectory 21 and which can damage these body components of the motor vehicle 1. The motor vehicle 1 is moving forward in the direction of travel 22. Thrown off particles 9 can hit the fender 5, the wheel arch 6, the side doors 23, the side sills 24, an underbody 25 and / or a rear apron 26 and damage the surfaces of these body components. If the motor vehicle 1 moves backwards against the direction of travel 22, then particles 9 can be thrown off in a similar manner to the forward movement, so that they hit the fender 5, the wheel arch 6, the side doors 23, the side sills 24, the underbody 25 and / or a front apron 27 of the motor vehicle 1 and damage the surfaces of these body components.Therefore, it may also be expedient to design the gravel detection device 2 in such a way that particles 9 stirred up during reversing are also detected.

[0156] Fig. 5 schematically shows two motor vehicles 1 in a side view, wherein at least the front motor vehicle 1 moves forward in the direction of travel 22 and trajectories 21 of ejected particles 9 generated by this movement, as well as the respective body components of the motor vehicles 1, which the ejected particles 9 can impact. The ejected particles 9 can impact the fender 5, the wheel arch 6, the underbody 25 and / or the rear apron 26 of the preceding motor vehicle 1, as well as the fender 5, the front apron 27, a hood 28 and / or a windshield 29 of the following motor vehicle 1.

[0157] The predetermined measures outlined above are summarized below. These predetermined measures include one or more of the following: - Issue a warning message, - maximum straightening of the wheels, - Adapting the steering wheel control to indirect steering transmission, - Reduction of driving speed, - Reduction of maximum drive torques, - Increasing the distance to the vehicle in front, - Check the lanes for gravel condition and change lanes if necessary, - Extension of a baffle plate, - Sending a message to other vehicles and / or to an external server, where the message describes the gravel condition.

[0158] The predetermined measures are initiated, reset, or withdrawn depending on the gravel condition of the roadway and the associated hazard to motor vehicle 1. They can be implemented individually or in combination, depending on the respective gravel condition or hazard level. The implementation of the measures is preferably determined empirically in advance. Reference symbol 1 motor vehicle 2 gravel detection device 3 Evaluation device 4 Vibration sensor 5 fenders 6 wheel arch 7 wheel 8 Outer body section 9 particles 10 Storage device 11 Speed ​​sensor 12 Display device 13 speakers 14 Sensor mat 15 Navigation device 16 Driver assistance system 17 Radio communication device 18 Actuator 19 baffle plate 20 Extension direction 21 Trajectory 22 Direction of travel 23 Side door 24 side skirts 25 Underbody 26 Rear apron 27 Front apron 28 Bonnet 29 Windshield

Claims

[1] Motor vehicle (1) with a gravel detection device (2), comprising a wheel (7) with a profiled tyre which is at least partially covered by a mudguard (5), a sensor (4, 14) mounted in an area of ​​the fender (5) for detecting stone impact, and an evaluation device (3) which, depending on one or more detected rockfalls, detects a gravel condition of a roadway to be traveled and which triggers a predetermined measure depending on the gravel condition. [2] Motor vehicle according to claim 1, characterized by that the sensor is a vibration sensor (4), in particular a sound sensor or a vibration sensor, or a pressure sensor. [3] Motor vehicle according to claim 2, characterized by that a sensor mat (14) is provided which comprises several of the pressure sensors. [4] Motor vehicle according to one of claims 1 or 2, characterized bythat the vibration sensor (4) is directly coupled to the fender for detecting structure-borne noise. [5] Motor vehicle according to one of claims 1 to 4, characterized by that the evaluation device (3) has a vibration analysis device with which vibration signals typical for stone chips are detected and evaluated as stone chips by the evaluation device (3). [6] Motor vehicle according to one of claims 1 to 5, characterized by that the motor vehicle (1) has a movable baffle plate (19) which is movable as a function of a stone impact detected by the gravel detection device (2). [7] Motor vehicle according to one of claims 1 to 6, characterized by that the motor vehicle (1) has an output device (12, 13) for outputting an optical and / or acoustic warning signal. [8] Method for detecting gravel for a motor vehicle (1) with a gravel detection device (2) which has a sensor (4, 14) for mounting in an area of ​​a fender (5) of the motor vehicle (1), wherein the fender (5) partially covers a profiled tire of a wheel (7) of the motor vehicle (1), and stone chips in the area of ​​the fender (5) are detected with the sensor (4, 14), and with an evaluation device (3) a gravel condition of a roadway to be traveled is detected as a function of one or more detected rockfalls and a predetermined measure is triggered as a function of the gravel condition. [9] Method according to claim 8, characterized by that the predetermined measure includes one or more of the following measures: - Issue a warning message, - maximum straightening of the wheels (7), - Adapting the steering wheel control to indirect steering transmission, - Reduction of driving speed, - Reduction of maximum drive torques, - Increasing the distance to the vehicle in front, - Checking lanes and changing lanes if necessary, - extending a baffle plate (19), - Sending a message to other vehicles and / or to an external server, where the message describes the gravel condition. [10] Method according to claim 8 or 9, characterized by that the evaluation device (3) triggers the predetermined measure depending on the intensity and / or frequency of detected stone chips. [11] Method according to one of claims 8 to 10, characterized by , that the evaluation device (3) records and stores a vibration signal generated by the sensor (4, 14) within a predetermined time interval or over a predetermined distance, and compares the stored vibration signal with stored vibration patterns of stone chips by means of a pattern comparison in such a way that it determines one or more vibration patterns similar to the vibration signal, wherein ballast conditions are assigned to the stored vibration patterns, so that the ballast condition of the roadway is determined on the basis of the ballast conditions of the similar vibration pattern(s). [12] Method according to one of claims 8 to 11, characterized by , that the evaluation device (3) records vibration pulses from individual stone impacts and links them to the vehicle speed, and several vibration pulses are statistically analyzed, in particular with regard to their frequency, average rockfall intensity and average rockfall speed, in order to determine the ballast condition from the statistical parameters determined therefrom. [13] Method according to one of claims 8 to 12, characterized by that a motor vehicle (1) is used with a gravel detection device (2) according to one of claims 1 to 7.

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